. I am not trusted in Firefox. Also tried on Safari on a Apple, it did not work. Did not work on my Android Phone either…

Probably because you are sending the Let’s Encrypt Authority X3 intermediate signed by ISRG Root X1. This intermediate does not have great compatibility with older/non-updated devices. Did you manually setup the certificate chain?

At the moment, you should be sending the Let’s Encrypt Authority X3 intermediate signed by DST Root CA X3. It has the greatest device compatibility.

**** I do notice >>> This site works only in browsers with SNI support.

This is really not an issue because your IP (the IP you host your website on) are not dedicated to only your website, and SNI (Server Name Indication * definitionfrom Wikipedia ) just means this / helps.

maccurt:

I am not trusted in Firefox. Also tried on Safari on a Apple, it did not work. Did not work on my Android Phone either…

That’s weird, because the ISRG Root X1 should be trusted in all platforms by now…

Also, browsers should be able to use the extra certificate reference (in the certificate) to draw another path to the more widely trusted (in older devices) certificate.

Could you please try to update your firefox… (If it’s not the latest version) ? (And if the update does not work, please tell us the old and new version).
Please also tell us your iPhone / Android OS version…

Ok, I update my firefox to 47.0.2 and I got this see below, but the updated prompted me to install yet another update, so I just downloaded it and installed it and got to Firefox Quantum 64 (64-bit) and it works now. I don’t have the Safari version now (at another location)… I will look into it. Let me try on a Android device… and I will get back to you… I really appreciate your help, and responding so soon…